Question #6a5d8

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Question #6a5d8

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Answer 1 · 2015-11-29T19:26:07

$"364 g " -> " lactose"$
$"196 g " -> " water"$

Explanation:

So, you know that your target solution has a total mass of $"560 g"$ , and that its percent concentration by mass is equal to $65%$ .

What that means is that every $"100 g"$ of solution must contain $"65 g"$ of solute. In your case, the target solution needs to contain $"65 g"$ of lactose per $"100 g"$ .

So, you know that

$color(blue)("% w/w" = "mass of solute"/"mass of solution" xx 100)$

If $x$ represents the mass of lactose needed to make this solution, you can say that you have

$( x )/"560 g" xx 100 = 65%$

The value of $x$ will come out to be

$x = (65 * "560 g")/100 = "364 g"$

Since the total mas of the solution is equal to $"560 g"$ , it follows that the mass of water needed to make this solution will be

$m_"sol" = m_"solute" + m_"solvent"$

$m_"water" = "560 g" - "364 g" = "196 g"$

Therefore, if you mix $"196 g"$ of water with $"364 g"$ of lactose, you will get a final solution that is $"65% w/w"$ lactose.

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Question #6a5d8

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